Adaptive Sagnac interferometer with dynamic population grating in saturable rare-earth-doped fiber

Abstract

Sagnac fiber interferometer with the dynamic population grating formed in the rare-earth doped fiber is proposed for homodyne adaptive detection of optical phase modulation. The configuration is shown to be a simple all-optical fiber sensor suitable for linear high sensitivity detection of mechanical vibrations, acoustic signals, thermo-optic effect etc. Theoretical consideration shows that the quadratic response of this interferometric configuration associated with the amplitude dynamic grating is observed in the reflected wave mainly, while the recorded phase grating results in the linear energy exchange between the transmitted and reflected from the Sagnac loop light waves. Experiments with the erbium- and ytterbium-doped fiber based adaptive Sagnac configurations (with the operation wavelengths 1485 and 1,064 nm respectively) of the fiber accelerometers confirmed these general conclusions and demonstrated sensitivity of the fiber based interferometric configurations (~3 10⁻⁵ rad/Hz¹/²) governed basically by the noise of the utilized lasers.

Advanced fiber-optic acoustic sensors

“…The fiber-optic Sagnac interferometer is also one of the most explored configurations for optical acoustic sensing [6,17]. This interferometer has been widely applied in the manufacture of fiber-optic hydrophone systems for acoustic detection.…”

“…Their preliminary works marked the beginning of fiber-optic acoustic sensing that, since then, continued to be developed. Currently, numerous works in this field can be found, many of these following interferometric configurations such as Mach-Zehnder [4], Michelson [5], Sagnac [6], and Fabry-Pérot [7], while others explore the possibilities offered by fiber Bragg grating (FBG) sensors [8]. A comprehensive review paper in this area until 2008 was written by Graham et al [9], and another work comparing three different types of fiber-optic acoustic sensors was published in 2010 [10].…”

Brillouin-like effects in rare-earth-doped bi-directional optical fiber amplifiers

“…In open-cavity fiber lasers, the slowly-moving dynamical population inversion gratings inscribed in an active medium by intracavity radiation have a reverse effect on the inscribing waves via feedback they provide leading to so called "mode-pulse" laser operation different from mode-locked and Q-switched laser regimes 11,12 . Among other PIDG applications are adaptive interferometry 13,14 and nonlinear filtering enabling narrowband operation of semiconductor and fiber laser configurations [15][16][17][18] .…”

Fibre Bragg Grating-Based Cascaded Acoustic Sensors for Potential Marine Structural Condition Monitoring

“…The majority of optical fibre acoustic sensors to date have been based on interferometric configurations such as using Mach-Zahnder [8], Michelson [9], Fabry-Perrot [10] or Sagnac [11] techniques. Recently, distributed feedback (DFB) fibre lasers have been applied to this field (and their use has been reported elsewhere [12]).…”